This invention relates to the field of integrated circuit packaging, particularly to light modulator packaging, and more particularly to windows for digital micromirror device packages.
Micromechanical devices are small structures typically fabricated on a semiconductor wafer using techniques such as optical lithography, metal sputtering, and plasma etching which have been developed for the fabrication of integrated circuits.
Digital micromirror devices (DMDs), sometimes referred to as deformable micromirror devices, are a particular type of micromechanical devices. Other types of micromechanical devices include accelerometers, pressure and flow sensors, gears and motors. While some micromechanical devices, such as pressure sensors, flow sensors, and DMDs have found commercial success, other types have not yet been commercially viable.
Digital micromirror devices are primarily used in optical display systems. In display systems, the DMD is a light modulator which uses digital image data to modulate a beam of light by selectively reflecting portions of the beam of light to a display screen. While analog modes of operation are possible, DMDs are typically operated in a digital bistable mode of operation and as such are the core of the first true digital full-color image projection systems.
Micromirror devices are used to create image displays by selectively reflecting light from the micromirrors. Micromirror devices are also very sensitive to contamination from outside particles, therefore they must be contained in a sealed environment to protect the micromirror device from the outside particles. Additionally, the micromirror package must have a precisely formed window in the package to allow light to reach the micromirror device and reflect therefrom out of the package.
Micromechanical devices in general, and micromirror device in particular, often require nontraditional packages in order fully to operate to their full potential. These special packages raise the finished cost of the device, and often cost more than the device they package. Perhaps the best example of a micromechanical device that requires special packaging is a micromirror device. Because of the strict optical constraints placed on the package window, prior art windows for micromirror assemblies are very expensive to manufacture. Therefore, an improved low-cost window for a micromechanical device is needed.
Objects and advantages will be obvious, and will in part appear hereinafter and will be accomplished by the present invention which provides a method and system for an improved windowed package lid. One embodiment of the claimed invention provides a method of packaging a device comprising the steps of providing a ceramic package substrate defining a central region, attaching a metal sealing ring to the ceramic package substrate, bonding the device to the central region of the ceramic package substrate, gluing a window to a window frame, and welding the window frame to the sealing ring.
Another embodiment of the present invention provides a micromechanical package lid. The package lid comprises a glass window and a metal window frame glued to said glass window. Typical package lids also have at least one anti-reflective coating on said glass window. Typical package lids also have a metal aperture deposited on said glass window.
Another embodiment of the disclosed invention provides a device package comprising a substrate having a central region, a sealing ring on the substrate around the central region, a device attached to the central region of the substrate, a window frame attached to the sealing ring, and a window glued to the window frame. The device package has an inner chamber enclosing the device formed by the substrate, sealing ring, window frame, and window.
Yet another embodiment of the disclosed invention provides a projection display system. The projection display system comprises a light source for projecting a beam of light along a light path, a spatial light modulator device in the light path for selectively reflecting portions of the beam of light along the projection light path, and projection optics along said projection light path for focusing said selectively reflected portions of said beam of light onto an image plane.
The spatial light modulator device in the disclosed projection display system is comprised of a micromechanical spatial light modulator packaged within a chamber created by a ceramic substrate, a sealing ring attached to said ceramic substrate, a window frame attached to the sealing ring, and a glass window glued to the sealing ring.